Pi Font

Definition

A font of special characters such as mathematical symbols, dingbats, or other non-alphabetic sorts not found in a standard text font. Pi fonts are used to supplement regular typefaces with specialised characters. The name derives from the traditional printer's term "pi" for mixed or disordered type.

Source

Robert Bringhurst — p. 328:
A font of special characters such as mathematical symbols, dingbats, or other non-alphabetic sorts.